1. Technical Field
The subject invention relates to a heat treating assembly and a method for altering a defined area of a substrate with laser energy.
2. Related Art
Various heat treating assemblies are known to those skilled in the art that employ lasers and that use laser energy to treat a substrate. One drawback of treating the substrate with the laser is that once the laser emits the laser energy as a beam, it is difficult to restrict the energy to an area of treatment. The laser energy once absorbed by the substrate has a tendency to be conducted by the material of the substrate to regions beyond the areas directly exposed to the laser energy. This conduction makes it difficult it to precisely control the area of treatment. Known laser treatment systems also employ a relatively narrow beam of light in relation to the area to be treated in an effort to control the application of the laser energy to the desired area. Such a thin beam approach commonly requires that multiple passes (known as rastering) be made in a pattern scanning the area from side to side in lines from top to bottom. This approach is complex and costly, especially when there are multiple areas to be scanned and still does not avoid the problems associated with the controlling of the conduction of the laser energy beyond the intended target area near the boundaries.
Cross-sectional views of substrates 10, 12 that have been treated in accordance with the prior art methods are illustrated in FIGS. 1 and 2. The substrates 10, 12, after being treated with the laser, were sectioned and mounted for viewing to observe the alteration of the substrates 10, 12. Each of the substrates 10, 12 include a horizontal surface 14 and a vertical surface 16. The substrates 10, 12 were treated to harden the horizontal surface 14 while the vertical surface 16 was not to be hardened. The laser energy was focused on the horizontal surface 14, but once the substrates 10, 12 absorbed the laser energy, the heat generated was conducted from the horizontal surface 14 to the vertical surface 16. The conduction of the heat energy results in the vertical surface 16 being hardened, which may be detrimental to the usefulness of the substrates 10, 12. As shown in FIGS. 1 and 2, the treated area slopes downwardly from the horizontal surface 14 toward the vertical surface 16.
The substrate 10 in FIG. 1 may be, for example, a steel piston and the horizontal surface 14 to be hardened may be a groove on the steel piston. The vertical surface 16 of the steel piston, if repeatedly stressed, may be prone to fatigue and possible failure as a result of being heat treated and hardened from the conduction of heat beyond the desired area. Prior art FIG. 2 illustrates another example in which an iron scraper ring is provided as the substrate 12 having the horizontal surface 14 to be treated. Again, the heat energy has been conducted from the horizontal surface 14 to the vertical surface 16 and the vertical surface 16 has been detrimentally hardened. For the same reasons stated above, it is disadvantageous to have the vertical surface 16 hardened.
Yet another disadvantage of the related art methods and assemblies is that the substrate has a tendency to be distorted after it has been treated. The surface areas of the substrate have stresses such that treatment of the areas increases the stresses and the substrate can become distorted. As an example, a piston ring has stresses as a result of the shape of the piston ring. When the piston ring is treated with the related art methods and assemblies, the piston ring has a tendency to bend and become distorted.